Temperature and Moisture Compensation on Three-Wire Capacitive Sensors for Air Bag Applications

Air bags have saved many lives. Nevertheless as they use pyrotechnic inflating devices, they can prove to be dangerous in some identified positional conditions. Furthermore, the strength used to inflate the bag must match the passenger morphology so as not to hurt him. Therefore morphological estimation and position monitoring is required for the Static or Dynamic Automatic Suppression of the new FMVSS208 regulation. The Faurecia BioVolume sensing system uses capacitive sensors to perform both monitoring and morphological estimation. This technology presents many advantages such as low cost and easiness of integration but presents some drawbacks amongst them is their sensibility to temperature and humidity[1]. In this paper the authors show that it is possible to get rid of the drifts induced by temperature and moisture with the three-wire probe technology[2] implemented in BioVolume.